Y khoa, y dược - The central nervous system: Part B

12 The Central Nervous System: Part BLateralization of Cortical FunctionLateralization Division of labor between hemispheresCerebral dominanceDesignates the hemisphere dominant for language (left hemisphere in 90% of people)Lateralization of Cortical FunctionLeft hemisphere Controls language, math, and logicRight hemisphereInsight, visual-spatial skills, intuition, and artistic skillsLeft and right hemispheres communicate via fiber tracts in the cerebral white matterCerebral White MatterMyelinated fibers and their tractsResponsible for communication Commissures (in corpus callosum)—connect gray matter of the two hemispheres Association fibers—connect different parts of the same hemisphereProjection fibers—(corona radiata) connect the hemispheres with lower brain or spinal cordFigure 12.10aCorona radiataProjectionfibers Longitudinal fissureGray matterWhite matterAssociationfibersLateralventricle FornixThirdventricleThalamusPonsMedulla oblongataDecussationof pyramidsCommissuralfibers (corpus callosum) Internalcapsule SuperiorBasal nuclei• Caudate• Putamen• Globuspallidus (a) Basal Nuclei (Ganglia)Subcortical nucleiConsists of the corpus striatumCaudate nucleusLentiform nucleus (putamen + globus pallidus)Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain) Figure 12.11aFibers ofcorona radiataCorpusstriatum(a) Projection fibersrun deep to lentiform nucleusCaudatenucleus ThalamusTail ofcaudatenucleusLentiformnucleus• Putamen• Globus pallidus (deep to putamen)Figure 12.11b (1 of 2)Corpus callosumAnterior hornof lateral ventricleCaudate nucleusPutamenLentiformnucleus(b) Globuspallidus ThalamusTail of caudate nucleusThird ventricleCerebral cortexCerebral white matterAnteriorPosteriorInferior hornof lateral ventricleFigure 12.11b (2 of 2)Corpus callosumAnterior hornof lateral ventricleCaudate nucleusLentiform nucleus(b) ThalamusThird ventricleCerebral cortexCerebral white matterInferior hornof lateral ventricleFunctions of Basal NucleiThough somewhat elusive, the following are thought to be functions of basal nucleiInfluence muscular control Help regulate attention and cognitionRegulate intensity of slow or stereotyped movementsInhibit antagonistic and unnecessary movementsDiencephalonThree paired structuresThalamusHypothalamusEpithalamusEncloses the third ventriclePLAYAnimation: Rotatable brain (sectioned)Figure 12.12Corpus callosumChoroid plexusThalamus(encloses third ventricle)Pineal gland(part of epithalamus)Posterior commissureCorporaquadrigeminaCerebralaqueductArbor vitae (ofcerebellum)Fourth ventricleChoroid plexusCerebellumSeptum pellucidumInterthalamicadhesion(intermediatemass of thalamus)Interven-tricularforamenAnteriorcommissureHypothalamusOptic chiasmaPituitary glandCerebral hemisphereMammillary bodyPonsMedulla oblongataSpinal cordMid-brainFornixThalamus80% of diencephalonSuperolateral walls of the third ventricleConnected by the interthalamic adhesion (intermediate mass)Contains several nuclei, named for their locationNuclei project and receive fibers from the cerebral cortexFigure 12.13aDorsal nucleiMedialAnteriornucleargroupReticularnucleusVentralanteriorVentrallateralVentralpostero-lateralLateralgeniculatebodyMedialgeniculatebodyPulvinarLateraldorsalLateralposterior(a) The main thalamic nuclei. (The reticular nuclei that “cap” thethalamus laterally are depicted as curving translucent structures.) Ventral nucleiThalamic FunctionGateway to the cerebral cortexSorts, edits, and relays informationAfferent impulses from all senses and all parts of the bodyImpulses from the hypothalamus for regulation of emotion and visceral function Impulses from the cerebellum and basal nuclei to help direct the motor corticesMediates sensation, motor activities, cortical arousal, learning, and memoryHypothalamusForms the inferolateral walls of the third ventricleContains many nucleiExample: mammillary bodiesPaired anterior nuclei Olfactory relay stationsInfundibulum—stalk that connects to the pituitary glandFigure 12.13bPreopticnucleusSupraopticnucleusSupra-chiasmatic nucleusAnteriorhypothalamicnucleusDorsomedialnucleusParaventricularnucleusFornixAnteriorcommissurePosteriorhypothalamicnucleusLateralhypothalamicareaVentromedialnucleusOpticchiasmaInfundibulum(stalk of thepituitary gland)PituitaryglandMammillarybody(b) The main hypothalamic nuclei.ArcuatenucleusHypothalamic FunctionAutonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility)Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drivesHypothalamic FunctionRegulates body temperature, food intake, water balance, and thirstRegulates sleep and the sleep cycleControls release of hormones by the anterior pituitaryProduces posterior pituitary hormonesEpithalamusMost dorsal portion of the diencephalon; forms roof of the third ventriclePineal gland—extends from the posterior border and secretes melatoninMelatonin—helps regulate sleep-wake cyclesFigure 12.12Corpus callosumChoroid plexusThalamus(encloses third ventricle)Pineal gland(part of epithalamus)Posterior commissureCorporaquadrigeminaCerebralaqueductArbor vitae (ofcerebellum)Fourth ventricleChoroid plexusCerebellumSeptum pellucidumInterthalamicadhesion(intermediatemass of thalamus)Interven-tricularforamenAnteriorcommissureHypothalamusOptic chiasmaPituitary glandCerebral hemisphereMammillary bodyPonsMedulla oblongataSpinal cordMid-brainFornix Brain StemThree regionsMidbrainPonsMedulla oblongata Brain StemSimilar structure to spinal cord but contains embedded nucleiControls automatic behaviors necessary for survivalContains fiber tracts connecting higher and lower neural centersAssociated with 10 of the 12 pairs of cranial nervesFigure 12.14Frontal lobeOlfactory bulb(synapse point ofcranial nerve I)Optic chiasmaOptic nerve (II)Optic tractMammillary bodyPonsMedullaoblongataCerebellumTemporal lobeSpinal cordMidbrainFigure 12.15aOptic chiasmaView (a) Optic nerve (II)Mammillary bodyOculomotor nerve (III)Crus cerebri ofcerebral peduncles (midbrain)Trigeminal nerve (V)Abducens nerve (VI)Facial nerve (VII)Vagus nerve (X)Accessory nerve (XI)Hypoglossal nerve (XII)Ventral root of firstcervical nerve Trochlear nerve (IV)PonsMiddle cerebellarpedunclePyramidDecussation of pyramids(a) Ventral viewSpinal cordVestibulocochlearnerve (VIII) Glossopharyngeal nerve (IX)Diencephalon• Thalamus• HypothalamusDiencephalonBrainstemThalamusHypothalamusMidbrain PonsMedullaoblongata Figure 12.15bView (b) Crus cerebri ofcerebral peduncles (midbrain)InfundibulumPituitary glandTrigeminal nerve (V)Abducens nerve (VI)Facial nerve (VII)Vagus nerve (X)Accessory nerve (XI)Hypoglossal nerve (XII)Pons(b) Left lateral viewGlossopharyngeal nerve (IX)DiencephalonBrainstemThalamusHypothalamusMidbrain PonsMedullaoblongata ThalamusSuperior colliculusInferior colliculusTrochlear nerve (IV)Superior cerebellar peduncleMiddle cerebellar peduncleInferior cerebellar peduncleVestibulocochlear nerve (VIII)OliveFigure 12.15cView (c)DiencephalonBrainstemThalamusHypothalamusMidbrain PonsMedullaoblongata Pineal glandDiencephalonAnterior wall offourth ventricle(c) Dorsal viewThalamusDorsal root offirst cervical nerveMidbrain• Superiorcolliculus• Inferiorcolliculus• Trochlear nerve (IV)• Superior cerebellar peduncleCorporaquadrigeminaof tectumMedulla oblongata• Inferior cerebellar peduncle• Facial nerve (VII)• Vestibulocochlear nerve (VIII)• Glossopharyngeal nerve (IX)• Vagus nerve (X)• Accessory nerve (XI)Pons• Middle cerebellar peduncleDorsal median sulcusChoroid plexus(fourth ventricle)MidbrainLocated between the diencephalon and the ponsCerebral peduncles Contain pyramidal motor tractsCerebral aqueductChannel between third and fourth ventriclesMidbrain NucleiNuclei that control cranial nerves III (oculomotor) and IV (trochlear)Corpora quadrigemina—domelike dorsal protrusions Superior colliculi—visual reflex centers Inferior colliculi—auditory relay centersSubstantia nigra—functionally linked to basal nucleiRed nucleus—relay nuclei for some descending motor pathways and part of reticular formationFigure 12.16aDorsalCerebral aqueductSuperiorcolliculusReticular formationCrus cerebri ofcerebral peduncle VentralFibers ofpyramidal tractSubstantianigra(a) MidbrainRednucleus Mediallemniscus Oculomotornucleus (III) Periaqueductal graymatterTectumPonsForms part of the anterior wall of the fourth ventricleFibers of the ponsConnect higher brain centers and the spinal cordRelay impulses between the motor cortex and the cerebellumOrigin of cranial nerves V (trigeminal), VI (abducens), and VII (facial)Some nuclei of the reticular formationNuclei that help maintain normal rhythm of breathing Figure 12.16bReticularformationTrigeminalnerve (V)PontinenucleiFibers ofpyramidaltractMiddlecerebellarpeduncleTrigeminal mainsensory nucleus Trigeminalmotor nucleus Superior cerebellarpeduncle Medial lemniscusFourthventricle(b) PonsMedulla OblongataJoins spinal cord at foramen magnumForms part of the ventral wall of the fourth ventricleContains a choroid plexus of the fourth ventriclePyramids—two ventral longitudinal ridges formed by pyramidal tractsDecussation of the pyramids—crossover of the corticospinal tractsMedulla OblongataInferior olivary nuclei—relay sensory information from muscles and joints to cerebellumCranial nerves VIII, X, and XII are associated with the medullaVestibular nuclear complex—mediates responses that maintain equilibriumSeveral nuclei (e.g., nucleus cuneatus and nucleus gracilis) relay sensory informationMedulla OblongataAutonomic reflex centersCardiovascular centerCardiac center adjusts force and rate of heart contractionVasomotor center adjusts blood vessel diameter for blood pressure regulationMedulla OblongataRespiratory centersGenerate respiratory rhythmControl rate and depth of breathing, with pontine centersMedulla OblongataAdditional centers regulateVomiting Hiccuping Swallowing CoughingSneezingFigure 12.16cChoroidplexusFourth ventriclePyramidMedial lemniscusInferior olivarynucleus Nucleusambiguus Inferior cerebellarpeduncle Cochlearnuclei (VIII) Vestibular nuclearcomplex (VIII) SolitarynucleusDorsal motor nucleusof vagus (X) Hypoglossal nucleus (XII)(c) Medulla oblongataLateralnucleargroupMedialnucleargroupRaphenucleusReticular formationThe Cerebellum11% of brain massDorsal to the pons and medullaSubconsciously provides precise timing and appropriate patterns of skeletal muscle contractionAnatomy of the CerebellumTwo hemispheres connected by vermisEach hemisphere has three lobesAnterior, posterior, and flocculonodular Folia—transversely oriented gyriArbor vitae—distinctive treelike pattern of the cerebellar white matterFigure 12.17b(b)Medullaoblongata Flocculonodularlobe Choroidplexus offourth ventriclePosteriorlobe Arborvitae Cerebellar cortexAnterior lobeCerebellarpeduncles• Superior• Middle• InferiorFigure 12.17d(d)AnteriorlobePosteriorlobeVermis(d)Cerebellar PedunclesAll fibers in the cerebellum are ipsilateralThree paired fiber tracts connect the cerebellum to the brain stemSuperior peduncles connect the cerebellum to the midbrainMiddle peduncles connect the pons to the cerebellumInferior peduncles connect the medulla to the cerebellumCerebellar Processing for Motor ActivityCerebellum receives impulses from the cerebral cortex of the intent to initiate voluntary muscle contractionSignals from proprioceptors and visual and equilibrium pathways continuously “inform” the cerebellum of the body’s position and momentumCerebellar cortex calculates the best way to smoothly coordinate a muscle contractionA “blueprint” of coordinated movement is sent to the cerebral motor cortex and to brain stem nucleiCognitive Function of the CerebellumRecognizes and predicts sequences of events during complex movementsPlays a role in nonmotor functions such as word association and puzzle solving